Massimiliano Biagini

Different carbon sources affect lifespan and protein redox state during Saccharomyces cerevisiae chronological ageing

Abstract.In this study, a proteomic approach that combines selective labelling of proteins containing reduced cysteine residues with two-dimensional electrophoresis/mass spectrometry was used to evaluate the redox state of protein cysteines during chronological ageing in Saccharomyces cerevisiae. The procedure was developed on the grounds that biotinconjugated iodoacetamide (BIAM) specifically reacts with reduced cysteine residues. BIAM-labelled proteins can then be selectively isolated by streptavidin affinity capture. We compared cells grown on 2% glucose in the exponential phase and during chronological ageing and we found that many proteins undergo cysteine oxidation. The target proteins include enzymes involved in glucose metabolism. Both caloric restriction and growth on glycerol resulted in a decrease in the oxidative modification. Furthermore, in these conditions a reduced production of ROS and a more negative glutathione half cell redox potential were observed.

The expression of low molecular weight protein tyrosine phosphatase is up‐regulated in 1,2‐dimethylhydrazine‐induced colon tumours in rats

Recent studies have assessed the role of low molecular weight protein tyrosine phosphatase (LMW‐PTP) in cell transformation and tumour onset and progression, observing a significant increase in the expression of LMW‐PTP mRNA and protein in human breast, colon, bladder and kidney tumour samples. Moreover, its enhanced expression is generally prognostic of a more aggressive cancer. To better understand the role of this protein during colon carcinogenesis and to study whether its overexpression is also observed in earlier phases of carcinogenesis, we studied its expression in colon tumours, induced in rats by treatment with 1,2‐dimethylhydrazine (DMH), an animal model that resemble the sequential formation of histopathological lesions of spontaneous carcinogenesis in humans. The results show a significant increase in LMW‐PTP expression in adenocarcinomas, suggesting that this phenomenon is associated with the onset of malignancy. Moreover a significant overexpression of LMW‐PTP transcript is associated with tumours originating in the proximal (right) part of the colon, confirming an observation already reported for human colon cancer.

Time-frequency MSE analysis of linear channel estimation methods for the LTE downlink

Orthogonal frequency-division multiplexing OFDM is widely used in modern communication systems thanks to the ease of its implementation as well as to a simple design of channel estimation methods. Pilot-based schemes are commonly employed to recover channel information and implement efficient channel equalisation. From the symbols transmitted over the pilot carriers, the channel coefficients for a whole OFDM are estimated. In this paper, we propose a method to compute in a closed form the mean square estimation error of different linear approximation and interpolation algorithms in the time-frequency domain. Specifically, by exploiting the linear relationship between the estimated channel coefficients for the whole frame and those relative to the pilots, the proposed approach permits to obtain the mean square error relative to all OFDM symbols in a frame. The method can be used for any linear frequency/time interpolation/approximation method and for any choice of pilot positions and channel statistics. Thanks to our derivations, several pilot-aided channel estimation and interpolation algorithms can be compared without resorting to burdensome computer simulations. In order to demonstrate the effectiveness of the method, the downlink of the long term evolution system is taken as a case study: some popular channel estimators have been selected and the best strategy in a realistic wireless scenario is investigated. The performance of the method is also verified by computing, by means of simulations, bit error rate BER curves for the long term evolution LTE multiple input multiple output MIMO downlink, using 2×2 and 4×4 Alamouti space-frequency coding configurations, in both uncoded and coded communications. Copyright

Comparison of channel estimation algorithms for MIMO downlink LTE systems

The definition of LTE and LTE-Advanced standards aims at improving the performance of cellular networks with the final goal of a fair competition between wired and wireless communication systems. In order to guarantee excellent performance, one of the crucial challenge to cope with is the introduction of advanced channel estimation techniques for Multiple Inputs Multiple Outputs (MIMO) systems. In this paper, we will review and compare several Pilot-Based Channel Estimation algorithms for MIMO LTE downlink communications. Channel estimation algorithms will be analysed for different multi-antenna schemes, namely 2×2 and 4×4 with Alamouti space-frequency coding. The performance of all of these schemes will be considered both for uncoded and coded systems. The simulation results will be obtained for a multipath fading channel, assuming high speed mobility for the mobile terminals.

Frame design for 5G multicarrier modulations

Orthogonal Frequency Division Multiplexing (OFDM) transmission technique has been considered for the 4G LTE-Advanced system because of its high performance and low complexity. In the new 5G scenario this type of modulation is not properly suited because of the additional requirements for very high spectral efficiency, low latency and low out-of-band (OOB) emissions. Thus, new waveforms have been chosen to replace it and effectively deal with these problems. Particularly, recently proposed multicarrier techniques as the Generalized Frequency Division Multiplexing (GFDM) and the Filter Bank Multicarrier (FBMC) modulations are two of the main candidates techniques for the new 5G standard. As for classical OFDM technique, the channel estimation is a crucial functionality for the all multicarrier approaches. In this paper we generalize a recently proposed method for the computation of the MSE on the time-frequency domain for pilot based channel estimation techniques in multicarrier system. This method permits to determine the most suitable channel estimation algorithm for a given wireless channel as well as to define the suitable pilot density in order to afford a target MSE value for a given SNR level. Hence, in this paper a general design tool for multicarrier systems is proposed.

Time-frequency MSE analysis for pilot aided channel estimation in OFDM systems

The objective of this paper is the derivation in a closed form of the channel estimation mean square error (MSE) expression in the time-frequency domain for OFDM systems, providing a general tool that can be applied to all linear channel estimation algorithms. The proposed method can be used to identify the best channel estimation algorithms, and to compare the different pilot symbol positioning strategies within an OFDM frame. Thanks to these features the proposed method can be used as a support to the system design.

Design of active noise control systems for pulse noise

Active noise control (ANC) methods have been successfully studied and tested for the cancellation of stationary noise. In the last decade, some adaptive solutions for the case of impulsive noise have been proposed in the literature. Nevertheless, such a model fits a limited class of impulsive disturbances that characterize practical scenarios. In this paper a preliminary study on the design of a non-adaptive deterministic ANC system for pulse signals that relies on no statistical assumptions is developed. The spatial audio rendering framework of Wave Field Synthesis is formally adopted in order to synthesize the cancelling sound field by means of an array of secondary sources. A set of preliminary simulations in free field environment, as well as the impact of array geometry and extension, has been carried out in view of forthcoming geometry and shape optimization of the system.

Active noise control for pulse signals by wave field synthesis

Active noise control (ANC) techniques have been intensively studied and applied for the cancellation of stationary noise. More recently, adaptive solutions for the case of impulsive noise, i.e. stochastic processes for which statistical moments superior to the first are not defined, have been proposed in the literature. Nevertheless, such a model fits a limited class of impulsive disturbances that could be experienced in practice. This paper introduces a preliminary study on a non-adaptive deterministic ANC technique for pulse signals that relies on no statistical assumptions. In particular, the spatial audio rendering framework of Wave Field Synthesis is formally adopted in order to synthesize the cancelling acoustic field. Simulations in free field environment, including the analysis of impairments such as time mismatch and template mismatch, have been carried out, showing promising performances in terms of noise cancellation.

Channel estimation MSE analysis for pilot aided OFDM systems

Since pilot based channel estimation techniques are commonly used in OFDM systems, the determination of the mean square error (MSE) in the time-frequency domain for these algorithms can provide an effective and general tool to be used to compare all the different approaches. The findings of this paper allow to determine the most suitable strategies for a given wireless channel and to identify the most appropriate symbol pattern within the OFDM frame. Therefore, the determination of the MSE is proven useful also in the system design.